1. Field
The present application relates to an optical element and a light emitting device including the same.
2. Background
A liquid crystal display (LCD) is a device which converts a variety of kinds of electrical information generated from various devices into visible information using a change in a liquid crystal transmittance according to an applied voltage, and transmits the visible information. The LCD needs back light because it does not have self-luminosity. Because the LCD consumes low power, has a light weight and a thin thickness, it is used widely. A backlight unit (BLU) serving as a light emitting device providing light should be provided at a rear surface of a liquid crystal panel on which an image is displayed.
The LCD includes the liquid crystal panel including a color filter substrate and an array substrate spaced a predetermined distance from each other to face each other, a liquid crystal layer interposed between the color filter substrate and the array substrate, and the BLU configured to irradiate the liquid crystal panel with light.
The BLU used in the LCD may be classified into an edge type and a direct type according to a position of a light emitting diode serving as a light source.
In the edge type BLU, the light emitting diodes serving as light sources are arranged at a side surface of a light guide panel, and the light guide panel irradiates to the liquid crystal panel with light radiated from the light emitting diodes through total reflection or the like.
In the direct type BLU, a diffusion plate is used instead of the light guide plate, and the light emitting diodes are disposed at a rear surface of the liquid crystal panel. Therefore, the light emitting diodes irradiate the rear surface of the liquid crystal panel with light.
Meanwhile, in the LCD, brightness uniformity is an important factor which determines quality of the LCD, and thus it is necessary for the BLU to uniformly irradiate the liquid crystal panel with the light.